This turned out to be a lot more work than I anticipated, but it is
definitely simpler (other than having #wizmakemap take achievements
away if you replace the level that contains the 'prize', which wasn't
handled before).
I cheated and made Mine's End into a no-bones level because the new
flagging scheme for luckstone, bag, and amulet can't carry over from
one game to another. It probably should have been no-bones all along.
Sokoban didn't have this issue because it's already no-bones.
Existing save files are invalidated.
